A filter is an oscillator used to delete some but not all of the spaceships in a stream. For example, a blocker can delete every second glider in a stream of period 8n+4, and can also do the same for LWSS streams. Other examples are the middleweight emulator, T-nosed p4 (either of which can be used to delete every second LWSS in a stream of period 4n+2) and the fountain (which does the same for MWSS streams).
| (click above to open LifeViewer)|
RLE: here Plaintext: here